The Testosterone and Thyroid Connection: How They Affect Each Other

An imbalance in testosterone or thyroid hormones could affect your mood, energy, libido, and health in the long run. Sometimes, the problem is both, because these hormones can interact with each other and cause overlapping symptoms. Here’s what to know about the link between testosterone and thyroid hormones.

About the Experts
Sarah Fishman, M.D., an endocrinologist at Premier Endocrine in New York City

Jose Flores, M.D., M.H.A., an assistant professor of urology at Weill Cornell Medicine

Diana Londono, M.D., a urologist at Emanate Health in Glendora, California

What Testosterone Does

Testosterone is a hormone that promotes muscle growth and regulates mood, libido, and energy in both men and women. Produced in the testes in men and the ovaries and adrenal glands in women, the hormone has widespread effects throughout the body.¹

“Testosterone is important for not only your sexual life but also your heart, brain, muscle, and bones,” says urologist Jose Flores, M.D.
Testosterone helps muscles repair after exercise,² activates brain cells involved in producing the feel-good chemical serotonin,³ and more. And while men make about 15 times more testosterone than women,⁴ testosterone helps women maintain their energy levels, libido, and muscle and bone strength as they age.⁵

What Your Thyroid Controls

Your thyroid gland produces hormones that help regulate metabolism, body temperature, blood pressure, heart rate, bone density, digestion, and, in women, ovulation frequency.⁶

The thyroid is butterfly-shaped and sits in the front of your neck just below your voice box. It makes two types of thyroid hormones: 

• Thyroxine (T4): This hormone plays a key role in heart and digestive function, metabolism, brain development, bone health, and muscle control. 80 percent of the thyroid gland’s output is T4. Thyroxine is considered inactive, meaning it has to be transformed by the liver and kidneys into T3 to be used by cells and organs throughout the body.⁷
• Triiodothyronine (T3): This hormone helps regulate metabolism, maintains muscle control, and improves brain, heart, and digestive functions. 

“Thyroid hormone affects your metabolic rate, so not only how quickly you process calories, but also how your body stores and uses energy,” says endocrinologist Sarah Fishman, M.D.

Does TRT Affect Thyroid?

Thyroid hormones usually stay within normal limits for clinically prescribed TRT. However, anabolic steroid abuse for sports or human chorionic gonadotropin (hCG) treatments to stimulate testosterone production might reduce circulating thyroid hormone levels.⁸

Always take TRT exactly as prescribed, and complete any blood work your doctor recommends.

If you have both a thyroid imbalance and low testosterone, your doctor might start by treating the thyroid problem. TRT might not be needed. “If the thyroid hormones are investigated and normalized, then the testosterone is going to kind of rebound on its own,” says Londono.

How Thyroid Function Affects Testosterone Levels

If your thyroid is out of balance, your testosterone levels can be, too—particularly in men. 

“There’s a lot of interplay between the hormones,” says Fishman. “They respond to each other.”

Your symptoms might depend on whether you have hyperthyroidism (your body is cranking out too much thyroid hormone) or hypothyroidism (thyroid production has slowed to a trickle).

Impact of hyperthyroidism on testosterone

Hyperthyroidism, or high thyroid hormone levels, can raise total testosterone by increasing SHBG, leaving less free testosterone to work in your body.⁹

However, people with high testosterone and hyperthyroidism might experience symptoms of hypogonadism (low testosterone), because more of their testosterone is bound to SHBG, meaning there’s less free testosterone in the body, Londono says.¹⁰

“If you don’t address the hyperthyroidism, then you can have higher SHBG, which hijacks and grabs the testosterone,” says Londono. Despite high circulating testosterone, you might feel like you have low testosterone because SHBG is holding onto it, she says. 

Excess SHBG can also increase the conversion of testosterone into estrogen.¹¹ This shift in the delicate balance of testosterone and estrogen can lead to irregular periods in women. In men, extra estrogen can cause sexual dysfunction and breast growth.¹²

Like hypothyroidism, hyperthyroidism has also been associated with reduced sperm counts.¹³ An excess of thyroid hormones might inhibit the proliferation of Sertoli cells, which support sperm production.

Impact of hypothyroidism on testosterone

Hypothyroidism, or low thyroid hormones, can reduce testosterone by decreasing levels of sex hormone-binding globulin (SHBG), a protein that binds to testosterone and makes it inactive.¹⁴ Only a small percentage is unbound or free testosterone, meaning it’s free to work directly in your body. 

When you don’t make enough thyroid hormones and don’t have enough SHBG, your total testosterone levels can drop. However, your free testosterone levels might still be in the normal range, says Fishman. With normal levels of this active form of testosterone, you might not feel symptoms of low testosterone.

• In men, severe hypothyroidism can impair the Leydig cells in the testes, which help produce testosterone, she adds. Hypothyroidism has been linked to reduced sperm counts in part through its effects on Leydig cells.¹⁵ 
• In women, hypothyroidism is linked with reduced SHBG and testosterone levels that are associated with an elevated risk of depression.¹⁶ Hypothyroidism is also linked with a higher risk of pregnancy complications.¹⁷

Hypothyroidism also disrupts other testosterone biomarkers. In both men and women, hypothyroidism can also decrease secretion of gonadotropin-releasing hormone (GnRH), which signals the production of testosterone precursors like luteinizing hormone (LH) and follicle-stimulating hormone (FSH).^{18 19}

“It can cause low testosterone because it just messes up the signal [from GnRH],” says urologist Diana Londono, M.D.

A combination of low thyroid and low testosterone could also result from a problem in the pituitary gland. 
“Somebody might have hypothyroidism because the thyroid is not being stimulated enough from the pituitary gland,” says Fishman. “And if that’s the case, then there’s much more of a reason to suspect that it [your pituitary] could be affecting testosterone production as well.”

Your pituitary gland, located at the base of your brain, releases thyroid-stimulating hormone, or TSH, to signal your thyroid to make T4 and T3. It also releases LH and FSH, which trigger testosterone production in the Leydig cells.²⁰ Anything that disrupts the function of your pituitary, such as a tumor, could interrupt this chain of events.

Levothyroxine (T4)

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Recognizing Symptoms of Hormonal Imbalances

Symptoms of a thyroid imbalance and low testosterone can overlap. Still, some symptoms might point to one condition more than the other, says Fishman.

Symptoms of low testosterone

Once testosterone is produced by the testes, ovaries, and adrenal glands, it enters the bloodstream and circulates through the body. Your body needs the right amount of testosterone to function at its best. Too much testosterone may lead to lower sperm counts; raised cholesterol, which can up your risk for high blood pressure; cardiac events like heart attacks; and liver damage. 

If your testosterone levels are below where they should be for your age, you may feel like you’re running on fumes and have symptoms like:

• Low energy
• Sleep issues
• Irritability
• Weight gain
• Depression 
• Loss of armpit and pubic hair
• Hot flashes
• Enlarged breast tissue
• Reduced muscle strength or endurance

Several factors may lead to low testosterone (typically anything below 300 ng/dL total testosterone), such as aging, genetics, and a wide range of health conditions. 

Symptoms of thyroid imbalances

Thyroid problems crop up more often than you’d think. About 5 percent of Americans have them, although it’s probably more. Research suggests they tend to be underdiagnosed.^{21 22}

Thyroid problems in men can often fly under the radar because the symptoms may be subtle and easily confused with other conditions. For example, weight gain can be related to a thyroid imbalance or too many wings and beer nights.

Women and men with thyroid problems may struggle with fatigue, muscle weakness, and skin issues. Men with thyroid issues may also face erectile dysfunction, premature ejaculation, and decreased testosterone levels. Women may notice irregular menstrual cycles.

• Hypothyroidism: When your thyroid gland creates less thyroid hormone than your body needs, your organs essentially slow down. You might feel tired, cold, or more forgetful. Your sex drive may wane. You may also notice symptoms like shortness of breath, dry skin, brittle hair and nails, high cholesterol, achy joints, muscle pain and weakness, weight gain, sleep problems, and depression.²³ Men might notice erectile dysfunction or premature ejaculation. Women often experience menstrual irregularities, such as infrequent or too-frequent periods, heavy periods, or missing periods.²⁴

• Hyperthyroidism: When there’s too much thyroid hormone in your body, your system tends to speed up. That can leave you feeling irritable, nervous, and anxious. And it can lead to physical symptoms like excessive sweating, weight loss despite an increased appetite, sensitivity to heat and cold, a rapid or irregular heartbeat, more frequent bowel movements, an enlarged thyroid gland, and difficulty sleeping. Hyperthyroidism can also cause irregular periods in women.²⁵

Overlapping thyroid and low testosterone symptoms

“The symptoms of low testosterone are often similar to the symptoms of low thyroid hormone,” says Fishman. The following symptoms could be a sign of low testosterone, low thyroid, or both, she says: 

• Low libido 
• Weight gain
• Fatigue

The similarity in symptoms for thyroid imbalance and low testosterone can make it hard to pinpoint the problem until you get your blood levels checked. But a few signs (or lack of signs) can be especially helpful clues. If you haven’t noticed any changes in body hair, then hypothyroidism is more likely than low testosterone, Fishman says. Poor muscle growth is more likely a sign of low testosterone than low thyroid, says Londono.

How to Support Testosterone and Thyroid Hormones

If you’re dealing with the symptoms of a thyroid or testosterone imbalance, blood tests can reveal whether your hormone levels are in range. 

When Flores checks a patient’s testosterone levels, he checks their thyroid levels, too. He estimates that low testosterone overlaps with a thyroid imbalance in about 10 percent of his patients, who tend to be over 50. He says the combination might be more common with aging. 

Ask your provider to check levels for your thyroid and a range of sex hormones: total testosterone, free testosterone, estrogen levels, follicle-stimulating hormone, luteinizing hormone, and sex-hormone binding globulin, says Fishman. 

“It’s really important to measure all the right things when you’re looking at testosterone production in general, and especially in the setting of hypothyroidism,” says Fishman.

Consider medication

Depending on your test results, your doctor might prescribe thyroid medication or hormone replacement therapy (HRT) to bring your hormones back into normal range. 

If your testosterone is low, you might receive testosterone replacement therapy (TRT), which can restore testosterone to normal levels and help correct symptoms such as low libido, depressed mood, and loss of muscle.
For hypothyroidism, you might be prescribed levothyroxine, a replacement thyroid hormone in pill form. For hyperthyroidism, your doctor might recommend medications or surgery to reduce your thyroid hormone levels.

Make positive lifestyle changes

A healthy lifestyle helps support your hormonal health for testosterone and thyroid. Try the following:

• Eat a healthy diet. Following a low-carb, Mediterranean-style diet might increase testosterone, perhaps by improving insulin sensitivity.²⁶
  
• Lift weights. “Weight training and building up muscle is really helpful,” says Fishman. Resistance training can speed up a sluggish metabolism (a common symptom of testosterone and low thyroid). It can also reduce inflammation that could otherwise harm your thyroid, she says.
  
• Prioritize sleep. Poor sleep can affect thyroid and testosterone levels—and exacerbate any existing fatigue. Investing in your sleep can help you feel better in the moment and over time. “When a male sleeps better, gets sleep apnea under control, sleeps eight hours, their testosterone is going to increase naturally,” says Flores. 

Support thyroid and testosterone with targeted supplements

Some research suggests dietary supplements could help support thyroid health and testosterone, although much of the research is preliminary. Here are some promising options: 

• Selenium: In one study, a combination of selenium (a mineral) and Myo-inositol (sugar alcohol) helped increase TSH levels in women with slightly low thyroid hormone levels.²⁷ Selenium has also been found to reduce autoimmune activity in Hashimoto’s thyroiditis, a condition that causes low thyroid levels.²⁸ Hone Health’s Thrive Thyroid Complex includes selenium and other supportive nutrients. 
• Ashwagandha and fenugreek: Research suggests that the herbs ashwagandha and fenugreek can help to increase testosterone levels in men levels.²⁹
• Vitamin D: This supplement hasn’t been shown to increase testosterone. But research suggests it might help ease some of the symptoms of low testosterone.³⁰

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About the author

Julie Stewart is a writer, editor, content strategist, and NASM-certified personal trainer. Her work has been published by leading consumer brands like Men’s Health, AARP The Magazine, EatingWell, Prevention, SELF, Everyday Health, Shape, WebMD, Medscape, and more.

About the reviewer

Dr. Robert Howe, M.D., is an obstetrician and gynecologist and a Reproductive Endocrinology and Infertility Specialist with experience treating osteoporosis, menopause, hypothyroidism, hormonal deficiencies in men and women, and other endocrine problems.